diff --git a/apps/dav/lib/CalDAV/CalDavBackend.php b/apps/dav/lib/CalDAV/CalDavBackend.php
index 2816c96e666d..087a65ac1bb6 100644
--- a/apps/dav/lib/CalDAV/CalDavBackend.php
+++ b/apps/dav/lib/CalDAV/CalDavBackend.php
@@ -1477,14 +1477,14 @@ public function createSchedulingObject($principalUri, $objectUri, $objectData) {
 	 */
 	protected function addChange($calendarId, $objectUri, $operation) {
 		$stmt = $this->db->prepare('INSERT INTO `*PREFIX*calendarchanges` (`uri`, `synctoken`, `calendarid`, `operation`) SELECT ?, `synctoken`, ?, ? FROM `*PREFIX*calendars` WHERE `id` = ?');
-		$stmt->execute([
+		$stmt->executeStatement([
 			$objectUri,
 			$calendarId,
 			$operation,
 			$calendarId
 		]);
 		$stmt = $this->db->prepare('UPDATE `*PREFIX*calendars` SET `synctoken` = `synctoken` + 1 WHERE `id` = ?');
-		$stmt->execute([
+		$stmt->executeStatement([
 			$calendarId
 		]);
 	}
diff --git a/lib/private/AppFramework/Db/Db.php b/lib/private/AppFramework/Db/Db.php
index c5c92f8f34cd..e7e4c9660d88 100644
--- a/lib/private/AppFramework/Db/Db.php
+++ b/lib/private/AppFramework/Db/Db.php
@@ -52,7 +52,7 @@ public function __construct(IDBConnection $connection) {
 	/**
 	 * @inheritdoc
 	 */
-	public function getQueryBuilder() {
+	public function getQueryBuilder(): IQueryBuilder {
 		return $this->connection->getQueryBuilder();
 	}
 
diff --git a/lib/private/DB/Connection.php b/lib/private/DB/Connection.php
index bbb97a7a30b4..0bd406180be5 100644
--- a/lib/private/DB/Connection.php
+++ b/lib/private/DB/Connection.php
@@ -36,6 +36,7 @@
 use Doctrine\DBAL\Driver\ServerInfoAwareConnection;
 use Doctrine\DBAL\Platforms\MySqlPlatform;
 use Doctrine\DBAL\Schema\Schema;
+use Doctrine\DBAL\Statement;
 use OC\DB\QueryBuilder\QueryBuilder;
 use OCP\DB\QueryBuilder\IQueryBuilder;
 use OCP\IDBConnection;
@@ -63,12 +64,7 @@ public function connect() {
 		}
 	}
 
-	/**
-	 * Returns a QueryBuilder for the connection.
-	 *
-	 * @return \OCP\DB\QueryBuilder\IQueryBuilder
-	 */
-	public function getQueryBuilder() {
+	public function getQueryBuilder(): IQueryBuilder {
 		return new QueryBuilder($this);
 	}
 
@@ -148,14 +144,6 @@ public function __construct(
 		parent::setTransactionIsolation(parent::TRANSACTION_READ_COMMITTED);
 	}
 
-	/**
-	 * Prepares an SQL statement.
-	 *
-	 * @param string $statement The SQL statement to prepare.
-	 * @param int $limit
-	 * @param int $offset
-	 * @return \Doctrine\DBAL\Driver\Statement The prepared statement.
-	 */
 	public function prepare($statement, $limit=null, $offset=null) {
 		if ($limit === -1) {
 			$limit = null;
@@ -181,7 +169,7 @@ public function prepare($statement, $limit=null, $offset=null) {
 	 * @param array                                       $types  The types the previous parameters are in.
 	 * @param \Doctrine\DBAL\Cache\QueryCacheProfile|null $qcp    The query cache profile, optional.
 	 *
-	 * @return \Doctrine\DBAL\Driver\Statement The executed statement.
+	 * @return Statement The executed statement.
 	 *
 	 * @throws \Doctrine\DBAL\DBALException
 	 */
diff --git a/lib/public/IDBConnection.php b/lib/public/IDBConnection.php
index 0b444cb6df8a..45ff04866cc9 100644
--- a/lib/public/IDBConnection.php
+++ b/lib/public/IDBConnection.php
@@ -35,6 +35,7 @@
 // This means that they should be used by apps instead of the internal ownCloud classes
 namespace OCP;
 use Doctrine\DBAL\Schema\Schema;
+use Doctrine\DBAL\Statement;
 use OCP\DB\QueryBuilder\IQueryBuilder;
 
 /**
@@ -47,17 +48,17 @@ interface IDBConnection {
 	/**
 	 * Gets the QueryBuilder for the connection.
 	 *
-	 * @return \OCP\DB\QueryBuilder\IQueryBuilder
+	 * @return IQueryBuilder
 	 * @since 8.2.0
 	 */
-	public function getQueryBuilder();
+	public function getQueryBuilder(): IQueryBuilder;
 
 	/**
 	 * Used to abstract the ownCloud database access away
 	 * @param string $sql the sql query with ? placeholder for params
 	 * @param int $limit the maximum number of rows
 	 * @param int $offset from which row we want to start
-	 * @return \Doctrine\DBAL\Driver\Statement The prepared statement.
+	 * @return Statement The prepared statement.
 	 * @since 6.0.0
 	 */
 	public function prepare($sql, $limit=null, $offset=null);
@@ -71,7 +72,7 @@ public function prepare($sql, $limit=null, $offset=null);
 	 * @param string $query The SQL query to execute.
 	 * @param string[] $params The parameters to bind to the query, if any.
 	 * @param array $types The types the previous parameters are in.
-	 * @return \Doctrine\DBAL\Driver\Statement The executed statement.
+	 * @return Statement The executed statement.
 	 * @since 8.0.0
 	 */
 	public function executeQuery($query, array $params = [], $types = []);